Antibacterial oral composition

ABSTRACT

An antibacterial oral composition effective to promote oral hygiene containing an antibacterial antiplaque agent and an additive which reduces staining of dental surfaces without substantially diminishing the antibacterial and antiplaque activity of the agent. Bis-biguanido hexanes, such as chlorhexidine and alexidine, and quaternary ammonium salts, such as benzethonium chloride and cetyl pyridinium chloride are typical examples of antibacterial agents. The antistain additive is a peroxydiphosphate salt, preferably tetrapotassium peroxydiphosphate (K 4  P 2  O 8 ).

This invention relates to an antibacterial oral composition which promotes oral hygiene.

Cationic nitrogen-containing antibacterial materials are well known in the art. See, for instance the section on "Quaternary Ammonium and Related Compounds" in the article on "Antiseptics and Disinfectants" in Kirk-Othmer Encyclopedia of Chemical Technology, second edition (Vol. 2, p. 632-635), incorporated herein by reference. Cationic materials which possess antibacterial activity (i.e. are germicides) are used against bacteria and have been used in oral compositions to counter plaque formation caused by bacteria in the oral cavity. Among the most common of these antibacterial anti-plaque quaternary ammonium compounds is benzethonium chloride, also known as Hyamine 1622 or diisobutylphenoxyethoxyethyl dimethyl benzyl ammonium chloride. In an oral preparation this material is highly effective in promoting oral hygiene by reducing formation of dental plaque and calculus, which is generally accompanied by a reduction in caries formation and periodontal diseases. Other cationic antibacterial agents of this type are those mentioned, for instance, in U.S. Pat. Nos. 2,984,639, 3,325,402, 3,431,208 and 3,703,583 and British Pat. No. 1,319,396.

Other antibacterial antiplaque quaternary ammonium compounds include those in which one or two of the substituents on the quaternary nitrogen has a carbon chain length (typically alkyl group) of some 8 to 20, typically 10 to 18, carbon atoms while the remaining substituents have a lower number of carbon atoms (typically alkyl or benzyl group), such as 1 to 7 carbon atoms, typically methyl or ethyl groups. Dodecyl trimethyl ammonium bromide, dodecyl dimethyl (2-phenoxyethyl) ammonium bromide, benzyl dimethyl stearyl ammonium chloride, cetyl pyridinium chloride and quaternized 5-amino-1,3-bis (2-ethyl-hexyl)-5-methyl hexa hydropyrimidine are exemplary of other typical quaternary ammonium antibacterial agents.

Other types of cationic antibacterial agents which are desirably incorporated in oral compositions to promote oral hygiene by reducing plaque formation are the amidines such as the substituted guanidines e.g. chlorhexidine and the corresponding compound, alexidine, having 2-ethylhexyl groups instead of chlorophenyl groups and other bis-biguanides such as those described in German patent application No. P 2,332,383 published Jan. 10, 1974, which sets forth the following formula: ##STR1## in which A and A' signify as the case may be either (1) a phenyl radical, which as substituent can contain up to 2 alkyl or alkoxy groups with 1 up to about 4C-atoms, a nitro group or a halogen atom, (2) an alkyl group which contains 1 to about 12C-atoms, or (3) alicyclic groups with 4 to about 12C-atoms, X and X' as the case may be may represent an alkylene radical with I-3C atoms, z and z' are as the case may be either zero or 1, R and R' as the case may be may represent either hydrogen, an alkyl radical with 1 to about 12C-atoms or an aralkyl radical with 7 to about 12C-atoms, n is a whole number of 2 to inclusively 12 and the polymethylene chain (CH₂) can be interrupted by up to 5 ether, thioether, phenyl- or naphthyl groups; these are available as pharmaceutically suitable salts. Additional substituted guanidines are: N'-(4-chlorobenzyl)-N⁵ -(2,4-dichlorobenzyl) biguanide; p-chlorobenzyl biguanide, 4-chlorobenzhydryl guanylurea; N-3-lauroxypropyl-N⁵ -p-chlorobenzyl biguanide; 5,6-dichloro-2-guanidobenzimidazole; and N-p-chlorophenyl-N⁵ -laurylbiguanide.

The long chain tertiary amines also possess antibacterial and antiplaque activity. Such antibacterial agents include tertiary amines having one fatty alkyl group (typically 12 to 18 carbon atoms) and 2 poly(oxyethylene) groups attached to the nitrogen (typically containing a total of from 2 to 50 ethenoxy groups per molecule) and salts thereof with acids and compounds of the structure: ##STR2## where R is a fatty alkyl group containing 12 to 18 carbon atoms and x, y and z total 3 or higher, as well as salts thereof. Generally, cationic agents are preferred for their antiplaque effectiveness.

The antibacterial antiplaque compound is preferably one which has an antibacterial activity such that its phenol co-efficient is well over 50, more preferably well above 100, such as above about 200 or more for S, aureus; for instance the phenol coefficient (A.O.A.C.) of benzethonium chloride is given by the manufacturer as 410, for S. aureus. The cationic antibacterial agent will generally be a monomeric (or possibly dimeric) material molecular weight well below 2,000, such as less than about 1,000. It is, however, within the broader scope of the invention to employ a polymeric cationic antibacterial agent. The cationic antibacterial is preferably supplied in the form of an orally acceptable salt thereof, such as the chloride, bromide, sulfate, alkyl sulfonate such as methyl sulfonate and ethyl sulfonate, phenylsulfonate, such as p-methylphenyl sulfonate, nitrate, acetate, gluconate, etc.

The nitrogen-containing cationic antibacterial agent and long chain tertiary amine antibacterial agents effectively promote oral hygiene, particularly by removing plaque. However, their use has been observed to lead to staining of dental surfaces or discoloration.

The reason for the formation of such dental stain has not been clearly established. However, human dental enamel contains a high proportion (about 95%) of hydroxyapatite (HAP) which includes CA⁺² and PO₄ ⁻³ ions. In the absence of dental plaque additional Ca⁺² and PO₄ ⁻³, particularly from saliva, can be deposited on the enamel and such deposits can include color bodies which ultimately stain the tooth enamel as a calcified deposit thereon. It can be that as the cationic or long chain tertiary amine antibacterial agents remove plaque they also denature protein from saliva in the oral environment and the denatured protein can then act as a nucleating agent which is deposited on and stains or discolors tooth enamel.

Previously employed additives which reduced dental staining by cationic antibacterial antiplaque agents also generally reduced the activity of antibacterial antiplaque agents such as bis-biguanido compounds, as by forming a precipitate with such agents.

It is an advantage of this invention that antinucleating additives, namely peroxydiphosphate salts, are provided which unexpectedly inhibit, i.e. prevent or remove, the staining of dental enamel caused by such cationic or long chain tertiary amine antibacterial agents without precipitating or substantially adversely affecting their antibacterial and antiplaque activity. In themselves (even in the absence of such antibacterial agents), these additives are effective to reduce formation of dental calculus without unduly decalcifying dental enamel, in addition to effectively inhibiting gingivitus. However, not all anti-nucleating agents are effective to prevent staining by such antibacterial agents. Victamide (also known as Victamine C) which is a condensation product of ammonia with phosphoruspentoxide, actually increases staining even in the absence of such antibacterial agents.

In accordance with certain of its aspects, this invention relates to an oral composition comprising an oral (orally acceptable) vehicle, at least one cationic or long chain tertiary amine antibacterial antiplaque agent which causes staining, and, as anti-staining additive, an effective stain-inhibiting amount of a peroxydiphosphate salt, preferably the tetrapotassium salt (K₄ P₂ O₈).

A number of peroxy compounds are known to be effective in preventing or removing the stain from teeth. Peroxymonosulfate (Oxone) is effective in reducing the intensity of dental stain. U.S. Pat. No. 3,988,433 discloses the use of organic peroxy acids to prevent or remove stain caused by Hibitane antibacterial agent. These aforementioned substances are, however, not desirable for use in the oral cavity since they are unstable in aqueous systems and since they release active oxygen too quickly (burst effect) which tends to damage the soft tissues in the oral cavity.

In U.S. Pat. No. 4,041,149 there is disclosed and claimed the use, per se, of these same peroxydiphosphate salts for controlling and preventing mouth odor. These salts are in themselves unusually stable in aqueous media, requiring the addition of the phosphatase enzymes found in saliva, in order to generate the peroxymonophosphate anion which is slowly hydrolyzed to hydrogen peroxide and orthophosphate at a rate directly proportional to the phosphatase concentration. Thus, extremely low phosphatase concentration can result in continuous generation of hydrogen peroxide and orthophosphate over a prolonged period, e.g. several months.

In addition, the peroxydiphosphate is substantive to oral surfaces and binds or reacts with the enamel surfaces of the teeth, i.e., the Ca⁺⁺ ions of the enamel, to provide for a longer lasting effect. The peroxydiphosphate has no initial burst effect of H₂ O₂ which leads to black, hairy tongue, because it releases H₂ O₂ at a slower rate. At equivalent concentrations of the peroxydiphosphate compound and hydrogen peroxide, it has one-tenth the amount of available oxygen compared to hydrogen peroxide. It is accordingly surprising that these peroxydiphosphates are unusually effective antistain additives as disclosed and claimed herein.

Any of the alkali metal peroxydiphosphates or their corresponding acid salts that are water-soluble to the extent of about 0.001 weight percent can be used in the compositions of this invention. Examples of these are potassium peroxydiphosphate (K₄ P₂ O₈), lithium peroxydiphosphate (Li₄ P₂ O₈) sodium peroxydiphosphate (Na₄ P₂ O₈), tripotassium monosodium peroxydiphosphate (K₃ NaP₂ O₈), dipotassium disodium peroxydiphosphate (K₂ Na₂ P₂ O₈ 2H₂ O), monopotassium trisodium peroxydiphosphate (KNa₃ P₂ O₈), monopotassium monosodium dihydrogen peroxydiphosphate (KNaH₂ P₂ O₈), trilithium monopotassium peroxydiphosphate (Li₃ KP₂ O₈), dilithium dipotassium peroxydiphosphate (Li₂ K₂ P₂ O₈), monolithium tripotassium peroxydiphosphate, (LiK₃ P₂ O₈), trilithium monosodium peroxydiphosphate, (Li₃ NAP₂ O₈), dilithium disodium peroxydiphosphate (Li₂ Na₂ P₂ O₈), monolithium trisodium peroxydiphosphate (LiNa₃ P₂ O₈), monolithium monosodium dihydrogen peroxydiphosphate (LiNaH₂ P₂ O₈), and monolithium monopotassium dihydrogen peroxydiphosphate (LiKH₂ P₂ O₈), in addition to dizinc peroxydiphosphate (Zn₂ P₂ O₈), tetraammonium peroxydiphosphate dihydrate (NH₄)₄ P₂ O₈ 2H₂ O), and the acid salts of group 2 metals such as barium dihydrogen peroxydiphosphate (BaH₂ P₂ O₈), calcium dihydrogen peroxydiphosphate (CaH₂ P₂ O₈), and the like.

The preferred tetrapotassium peroxydiphosphate is a stable, odorless, finely divided, free-flowing, white, non-hygroscopic crystalline solid having a molecular weight of 346.35 and an active oxygen content of 4.5%. The potassium peroxydiphosphate is 47-51% water-soluble at 0°-61° C., but insoluble in common solvents such as acetonitrile, alcohols, ethers, ketones, dimethyl formamide, dimethyl sulfoxide, and the like. A 2% aqueous solution has a pH of about 9.6 and a saturated solution thereof a pH of about 10.9. A 10% solution in water at 25° C. showed no active oxygen loss after four months; and at 50° C. a 10% solution showed an active oxygen loss of 3% in 6 months. This stability permits long shelf-like of oral compositions containing said peroxydiphosphate compound.

The concentration of these additives in oral compositions can range widely, typically upward from about 0.01% by weight with no upper limit except as dictated by cost or incompatibility with the vehicle. Generally, concentrations of about 0.01% to about 10% and preferably about 0.1% to 6% by weight are utilized. Oral compositions which in the ordinary course of usage could be accidentally ingested preferably contain lower concentrations of these additives. Thus, a mouthwash in accordance with this invention preferably contains less than about 1 weight % of the additive, preferably about 0.1-0.5 wt%. Dentrifice compositions, topical solutions and prophylactic pastes, the latter to be administered professionally, can preferably contain about 0.1 to 2 weight % of the additive. Most desirably the additive is present in a molar excess relative to the amount of antibacterial antiplaque agent (based on its free base form) in order to best minimize, inhibit or prevent staining.

Nitrogen-containing antibacterial agents which are cationic or long chain amine germicides which may be employed in the practice of this invention are described above. They are typically employed in amounts such that the oral product contains between about 0.001 and 15% by weight of the agent. Preferably for desired levels of antiplaque effect, the finished oral product contains about 0.01 to about 5%, and most preferably about 0.25 to 1.0% by weight of the antibacterial agent, referring to its free base form.

In certain highly preferred forms of the invention, the oral composition may be substantially liquid in character, such as a mouthwash or rinse. In such a preparation the vehicle is typically a water-alcohol mixture. Generally, the ratio of water to alcohol is in the range of from about 1:1 to about 20:1 preferably from 3:1 to 20:1 and most preferably about 17:3, by weight. The total amount of water alcohol mixture in this type of preparation is typically in the range of from about 70 to about 99.9% by weight of the preparation. The pH of such liquid and other preparations of the invention is generally in the range of from about 4.5 to about 9 and typically from about 5.5 to 8. The pH is preferably in the range of from about 6 to about 8.0. It is noteworthy that the compositions of the invention may be applied orally at a pH below 5 without substantially decalcifying dental enamel.

Such liquid oral preparations may also contain a surface active agent and/or a fluorine-providing compound.

In certain other desirable forms of this invention, the oral composition may be substantially solid or pasty in character, such as toothpowder, a dental tablet, a toothpaste or dental cream. The vehicle of such solid or pasty oral preparations contains polishing material. Examples of polishing materials are water-insoluble sodium metaphosphate, potassium metaphosphate, tricalcium phosphate, calcium pyrophosphate, magnesium orthophosphate, trimagnesium phosphate, calcium carbonate, alumina, hydrated alumina, aluminum silicate, zirconium silicates, silica, bentonite, and mixtures thereof. Preferred polishing materials include crystalline silica having particle sizes of up to 5 microns, a mean particle size of up to 1.1 microns, and a surface area of up to 50,000 cm² /gm. silica gel, complex amorphorus alkali metal aluminosilicate and hydrated alumina.

Alumina, particularly the hydrated alumina sold by Alcoa as C333, which has an alumina content of 64.9% by weight, a silica content of 0.008%, a ferric oxide content of 0.003%, and a moisture content of 0.37%, at 110° C., and which has a specific gravity of 2.42 and a particle size such that 100% of the particles are less than 50 microns and 84% of the particles are less than 20 microns, is particularly desirable.

When visually clear gels are employed, a polishing agent of colloidal silica, such as those sold under the trademark SYLOID as Syloid 72 and Syloid 74 or under the trademark SANTOCEL as Santocel 100 and alkali metal aluminosilicate complexes are particularly useful, since they have refractive indices close to the refractive indices of gelling agent-liquid (including water and/or humectant) systems commonly used in dentifrices.

Many of the so-called "water-soluble" polishing materials are anionic in character and also include small amounts of soluble material. Thus, insoluble sodium metaphosphate may be formed in any suitable manner, as illustrated by Thorpe's Dictionary of Applied Chemistry, Volume 9, fourth Edition, pp. 510-511. The forms of insoluble sodium metaphosphate known as Madrell's salt and Kurrol's salt are further examples of suitable materials. These metaphosphate salts exhibit a minute solubility in water, and therefore are commonly referred to as insoluble metaphosphates. There is present therein a minor amount of soluble phosphate material as impurities, usually a few percent such as up to 4% by weight. The amount of soluble phosphate material, which is believed to include a soluble sodium trimetaphosphate in the case of insoluble metaphosphate, may be reduced by washing with water if desired. The insoluble alkali metal metaphosphate is typically employed in powder form of a particle size such that no more than about 1% of the material is larger than 37 microns.

The polishing material is generally present in amounts ranging from about 20 to about 99% by weight of the oral preparation. Preferably, it is present in amounts ranging from about 20 to about 75% in toothpaste, and from about 70 to about 99% in toothpowder.

In the preparation of toothpowders, it is usually sufficient to admix mechanically, e.g., by milling, the various solid ingredients in appropriate quantities and particle sizes.

In pasty oral preparations the above-defined combination of the antibacterial antiplaque agent and additive should be compatible with the other components of the preparation. Thus, in a toothpaste, the liquid vehicle may comprise water and humectant typically in an amount ranging from about 10 to about 90% by weight of the preparation. Glycerine, sorbitol, or polyethylene glycol may also be present as humectants or binders. Particularly advantageous liquid ingredients are polyethylene glycol and polypropylene glycol. Also advantageous are liquid mixtures of water, glycerine and sorbitol.

In clear gels where the refractive index is an important consideration, about 3-30% by weight of water, 0 to about 80% by weight of glycerine, and about 20-80% by weight of sorbitol is preferably employed. A gelling agent, such as natural or synthetic gums or gumlike materials, typically Irish moss, sodium carboxymethylcellulose, methyl cellulose, hydroxyethyl cellulose, gum tragacanth, polyvinylpyrrolidone, starch, and preferably hydroxypropyl methyl cellulose and the Carbopols (e.g. 934,940 and 941). They are usually present in toothpaste in an amount up to about 10% by weight, preferably in the range of from about 0.5 to about 5%. In a toothpaste or gel, the liquids and solids are proportioned to form a creamy or gelled mass which is extrudable from a pressurized container or from a collapsible, e.g., aluminum or lead, tube.

The solid or pasty oral preparation which typically has a pH measured on a 20% slurry of about 4.5 to 9, generally about 5.5 to about 8 and preferably about 6 to about 8.0 may also contain a surface active agent and/or a fluorine-providing compound.

It will be understood that, as is conventional, the oral preparations are to be sold or otherwise distributed in suitable labelled packages. Thus a jar of mouthrinse will have a label describing it, in substance, as a mouthrinse or mouthwash and having directions for its use; and a toothpaste will usually be in a collapsible tube, typically aluminum or lined lead, or other squeeze dispenser for metering out the contents, having a label describing it, in substance, as a toothpaste or dental cream.

In oral compositions such as mouthrinses and toothpastes, a surfactant is often present, e.g. to promote foaming. It will be understood that it is preferable to employ nonionic surfactants rather than their anionic counterparts. Examples of water-soluble nonionic surfactants are condensation products of ethylene oxide with various reactive hydrogen-containing compounds reactive therewith having long hydrophobic chains (e.g. aliphatic chains of about 12 to 20 carbon atoms), which condensation products ("ethoxamers") contain hydrophilic polyoxyethylene moieties, such as condensation products of ethylene oxide with fatty acids, fatty alcohols and fatty amides including alcohols such as sorbitan monostearate or polypropyleneoxide (that is Pluronic materials).

In certain forms of this invention a fluorine-providing compound is present in the oral preparation. These compounds may be slightly soluble in water or may be fully water-soluble. They are characterized by their ability to release fluoride ions in water and by substantial freedom from reaction with other compounds of the oral preparation. Among these materials are inorganic fluoride salts, such as soluble alkali metal, alkaline earth metal and heavy metal salts, for example, sodium fluoride, potassium fluoride, ammonium fluoride, lead fluoride, a copper fluoride such as cuprous fluoride, zinc fluoride, a tin fluoride such as stannic fluoride or stannous chlorofluoride, barium fluoride, sodium fluorsilicate, ammonium fluorosilicate, sodium fluorozirconate, sodium monofluorophosphate, aluminum mono- and di-fluorophosphate, and fluorinated sodium calcium pyrophosphate. Alkali metal and tin fluorides, such as sodium and stannous fluorides, sodium monofluorophosphate and mixtures thereof, are preferred.

The amount of the fluorine-providing compound is dependent to some extent upon the type of compound, its solubility, and the type or oral preparation, but it must be a nontoxic amount. In a solid oral preparation, such as toothpaste or toothpowder, an amount of such compound which releases a maximum of about 1% by weight of the preparation is considered satisfactory. Any suitable minimum amount of such compound may be used, but it is preferable to employ sufficient compound to release about 0.005 to 1%, and preferably about 0.1% of fluoride ion. Typically, in the cases of alkali metal fluorides and stannous fluoride, this component is present in an amount up to about 2% by weight, based on the weight of the preparation, and preferably in the range of about 0.05 to 1%. In the case of sodium monofluorophosphate, the compound may be present in an amount up to 7.6% by weight, more typically about 0.76%.

In a liquid oral preparation such as a mouthwash, the fluorine-providing compound is typically present in an amount sufficient to release up to about 0.13%, preferably about 0.0013 to 0.1% and most preferably about 0.0013 to 0.05%, by weight, of fluoride ion.

Various other materials may be incorporated in the oral preparations of this invention. Examples are whitening agents, preservatives, silicones, chlorophyll compounds, and ammoniated material such as urea, diammonium phosphate, and mixtues thereof. These adjuvants, where present, are incorporated in the preparations in amounts which do not substantially adversely affect the properties and characteristics desired.

Any suitable flavoring or sweetening material may also be employed. Examples of suitable flavoring constituents are flavoring oils, e.g., oils of spearmint, peppermint, wintergreen, sassafras, clove, sage, eucalyptus, marjoram, cinnamon, lemon and orange, and methyl salicylate. Suitable sweetening agents include sucrose, lactose, maltose, sorbitol, sodium cyclamate, perillartine, APM and saccharine. Suitably, flavor and sweetening agents may together comprise from about 0.1 to 5% or more of the preparation.

In preparing the oral compositions of this invention comprising the above-defined combination of antibacterial agent and additive in an oral vehicle which typically includes water, it is highly preferred if not essential to add the additive after the other ingredients (except perhaps some of the water) are mixed or contacted with each other to avoid a tendency for said agent to be precipitated.

For instance, a mouthrinse or mouthwash may be prepared by mixing ethanol and water with flavoring oil, nonionic surfactant, humectant, cationic antibacterial antiplaque agent, such as benzethonium chloride or chlorohexidine, sweetener, color and then the abovedefined additive, followed by additional water as desired.

A toothpaste may be prepared by forming a gel with humectant, gum or thickener such as hydroxyethyl cellulose, sweetener and adding thereto polishing agent, flavor, antibacterial agent, such as benzethonium chloride or chlorhexidine, additional water, and then the above-defined additive. If sodium carboxymethyl cellulose is employed as the gelling agent, the procedure of either U.S. Pat. No. 3,842,168 or U.S. Pat. No. 3,843,779, modified by the inclusion of the additive, is followed.

In the practice of this invention an oral composition according to this invention such as a mouthwash or toothpaste containing cationic or long chain amine antibacterial antiplaque agent in an amount effective to promote oral hygiene and the defined additive in an amount effective to reduce staining of dental surfaces otherwise resulting from the presence of the antibacterial antiplaque agent, is applied regularly to dental enamel, preferably from about 5 times per week to about 3 times daily, at a pH of about 4.5 to about 9, generally about 5.5 to about 8, preferably about 6 to 8.

The following specific examples are further illustrative of the nature of the present invention, but it is understood that the invention is not limited thereto. All amounts and proportions referred to herein and the appended claims are by weight unless otherwise indicated.

Table I below is illustrative of mouthwash formulations according to the invention and the antistaining activity of the preferred K₄ P₂ O₈ additive therein. The tooth staining characteristics of the formulations are evaluated by slurrying hydroxyapatite (Biogel), a specific salivary protein, a carbonyl source (e.g. acetaldehyde), and a pH 7 phosphate buffer, with and without the mouthwash formulations being tested. The mixture is shaken at 37° C. for 18 hours. The colored HAP powder is separated by filtration, dried and the color levels (in reflectance units) determined on a Gardner color difference meter.

                                      TABLE I                                      __________________________________________________________________________     MOUTHWASH FORMULATIONS                                                                Placebo Control                                                         Example                                                                               (1)  (2)  (3)  (4)  (5)  (6)  (7)                                       __________________________________________________________________________     Ethanol                                                                               10%  10%  10%  10%  10%  10%  10%                                       Polyethylene                                                                          10   10   10   10   10   10   10                                        glycol 600                                                                     Flavor.sup.1                                                                          0.146                                                                               0.146                                                                               0.146                                                                               0.146                                                                               0.146                                                                               0.146                                                                               0.146                                     Saccharin                                                                             0.03 0.03 0.03 0.03 0.03 0.03 0.03                                      CPC.sup.2   0.1  0.1  0.1  0.1  0.1  0.1                                       K.sub.4 P.sub.2 O.sub.8                                                                         0.1  0.2  0.3  0.5  0.5                                       Phosphatase.sup.3                    0.1                                       Water, q.s. to                                                                        100  100  100  100  100  100  100                                       pH (3NHCl)                                                                            7.0  7.0  7.0  7.0  7.0  7.0  7.0                                       Reflectance                                                                           60.0 41.0 44.0 44.0 49.0 51.0 58.0                                      Difference                                                                            --   +19  -3.0 -3.0 -8.0 -10.0                                                                               -17.0                                     Rd                                                                                              |←COMPARED TO CPC→|             __________________________________________________________________________

1. Eugenol, Isoeugenol, Creosol or other specific flavor resistant to K₄ P₂ O₈. Flavors with phenol functional group preferred over C═O group.

2. Cetyl pyridinium chloride.

3. Worthington, acid enzyme phosphatase similar to enzyme in saliva.

The above results plainly establish that the peroxydiphosphate additives of the present invention, as exemplified by K₄ P₂ O₈, substantially reduce dental staining ordinarily produced by cationic quaternary ammonia antibacterial antiplaque agents as exemplified by CPC, and an even greater reduction in staining occurs in the presence of phosphatase enzyme as found in saliva. A K₄ P₂ O₈ concentration of about 0.5% appears to yield excellent results.

Further, in vitro tests establish that the antiplaque activity of Examples 2, 6 and 7 are substantially equal, indicating that the peroxydiphosphate additives of this invention do not significantly effect the antiplaque activity of CPC and the like.

Substitution of equivalent amounts of the following antibacterial antiplaque agents for the CPC employed in Examples 3-7 yield formulations also producing an unexpected reduction in dental staining.

    ______________________________________                                         Example    Antibacterial Antiplace Agent                                       ______________________________________                                          8         benzethonium chloride (BC)                                           9         chlorhexidine diacetate                                             10         chlorohexidine digluconate                                          11         dodecyl trimethyl ammonium                                                     bromide                                                             12         cetyl pyridinium chloride                                           13                                                                                         ##STR3##                                                           14         alexidine dihydrochloride                                           ______________________________________                                    

Table II below contains antistain and antigingivitus results of tests on 36 beagles, divided into 3 balanced groups. All dogs received complete dental prophylaxis in order to remove existing soft and hard dental deposits. The animals were kept on soft diet during the study. They were treated twice a day, 5 days a week with the indicated mouthwash formulations. The formulations were sprayed on all dentitions and mouths kept closed for 1 minute after each treatment. The placebo and control mouthwashes had the formulations of Example 1 and 2 above.

                  TABLE II                                                         ______________________________________                                                                         No.                                                                            Bleeding                                                   No.  Dogs with Staining                                                                            Units/                                                   Mean    Dogs   Mod-  Hea-       Total                                          Stain   w/o    erate vy         Units                                Example   Tooth   Stain  Only  Only Total at Risk                              ______________________________________                                         15 - Placebo                                                                             1.0     0/12   3/12  9/12 12/12 16/240                               16 - Control                                                                             0.7     0/12   3/12  9/12 12/12 21/240                               17-Control                                                                     + 1% K.sub.4 P.sub.2 O.sub.8                                                             0.4     7/12   1/12  4/12  5/12  3/240                               ______________________________________                                    

The above results plainly show that significant reduction in stain and bleeding are achieved by the formulation of Example 17 according to the invention relative to the placebo and control formulations.

The following formulations exemplify toothpastes with antiplaque activity and reduced staining.

    ______________________________________                                                           Example(Parts)                                                                 18   19      20                                              ______________________________________                                         Hydrated alumina    30     30      30                                          Polyethylene glycol 600                                                                            22     22      22                                          Pluronic F-108      3      3       3                                           Hydroxypropyl methyl cellulose                                                                     1.2    1.2     1.2                                         BC                  0.5    --      --                                          Hibitane            --     4.725   --                                          CPC                 --     --      0.5                                         K.sub.4 P.sub.2 O.sub.8                                                                            1.0    1.0     1.0                                         Sodium saccharin    0.17   0.17    0.17                                        Flavor              0.8    0.8     0.8                                         Water q.s. to       100    100     100                                         ______________________________________                                    

Significant reductions in dental staining and gingivitus are also obtained according to the present invention when the K₄ P₂ O₈ in the above examples is replaced by any of the other peroxydiphosphate salts disclosed above, particularly the alkali metal salts.

This invention has been described with respect to preferred embodiments and it will be understood that modifications and variations thereof obvious to those skilled in the art are to be included within the spirit and purview of this application and the scope of the appended claims. 

What is claimed is:
 1. In a method for reducing the amount of dental plaque in the oral cavity comprising applying to the oral cavity an oral composition having a pH of about 4.5 to about 9 and containing an oral vehicle and an effective plaque inhibiting amount of cetylpyridinium chloride or benzethonium chloride antibacterial antiplaque agent whose use has been observed to lead to staining or discoloration of dental surfaces, the improvement comprising including in said composition, as anti-stain additive, an effective stain-inhibiting amount of a peroxydiphosphate salt.
 2. A method according to claim 1 wherein said additive is tetrapotassium peroxydiphosphate.
 3. A method according to claims 1 or 2 wherein said antiplaque agent is cetylpyridinium chloride.
 4. A method according to claims 1 or 2 wherein said antiplaque agent is benzethonium chloride. 